[Xcb] [Semi-off-topic] Few questions regarding X programming

Barton C Massey bart at cs.pdx.edu
Fri Jan 18 19:46:10 PST 2008

In message <200801190304.32694.maximlevitsky at gmail.com> you wrote:
> But then the obvious question arises, how the X pixmaps are defined:
> I know that there are 3 formats: 
> XYBitmap - mono 'bitmap'
> XYPixmap - Internet sources suggest that it holds all red values of pixels  
> first, then all green values, and then the blue values - I will be glad to 
> hear more about it, I am just curios.
> ZPixmap - normal image, each pixel holds color information, but my question 
> is:
> Does ZPixmap hold RGB colors, or colormap indexes.
> If it holds RGB, then I probably will use the second method, I will 
> preallocate few colors, and use them to fill backgrounds, draw rectangles, 
> some decorations, and most drawing will be done using pixmaps.
> (Using MIT-SHM if available).

Pixmap formats don't really have anything to do with
colormaps.  Both XYPixmap and ZPixmap are alternate ways of
representing arrays of pixels, which may be indexes into a
colormap or may be true color values.  Don't use
XYPixmap---it's an anachronism and a mistake.

> Besides, all info about the bitmap formats is welcome.
> The X protocol spec seems to be sparse about it

See our new util/image library for an implementation of all
of it.

> 2) Can I ask more questions If I have them? :-)

You'll get better answers quicker on
xorg at lists.freedesktop.org.


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